TableView 单元格在滚动时消失 [英] TableView cell disappear on scroll
问题描述
我为这个问题找到了很多答案，但我不明白如何管理我的代码.当我滚动 tableView 内容时，单元格消失.我在单元格问答中只有两个文本.我尝试使用标识符(可重用)，但代码没有改变任何东西...
I found a lot of answer for this question but I don't anderstand how to manage my code. When I scroll the tableView content, the cell disappear. I just have two texts in the cell question and answer. I've tried to use an identifier (reusable) but the code doesn't change anything...
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
UILabel *textLabel = nil;
NSString* text = @"";
//static NSString *CellIdentifier = @"Cell";
NSString *CellIdentifier = [NSString stringWithFormat:@"%ld_%ld",(long)indexPath.section,(long)indexPath.row];
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
}
int y = -20;
float titleFontSize = 14.0f;
if(indexPath.row == 0) {
y = 0;
titleFontSize = 16.0f;
}
if(cell == nil)
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:@"Cell"];
textLabel = [[UILabel alloc] initWithFrame:CGRectZero];
[textLabel setLineBreakMode:NSLineBreakByWordWrapping];
[textLabel setMinimumFontSize:14.0f];
[textLabel setNumberOfLines:0];
[textLabel setFont:[UIFont systemFontOfSize:14.0f]];
[textLabel setTag:1];
[textLabel setTextColor:[UIColor colorWithRed:57/255.0 green:55/255.0 blue:64/255.0 alpha:1.0]];
// Titre
if(indexPath.row == 0) {
text = question;
[cell setBackgroundColor:[UIColor colorWithRed:220/255.0 green:224/255.0 blue:241/255.0 alpha:1.0]];//[UIColor colorWithRed:.945f green:.921f blue:.78f alpha:1]];
[textLabel setFont:[UIFont fontWithName:@"Helvetica-Bold" size:titleFontSize]];
}
// Contenu
else {
text = answer;
}
CGSize constraint = CGSizeMake(285, 20000.0f);
CGSize size = [text sizeWithFont:[UIFont systemFontOfSize:titleFontSize] constrainedToSize:constraint lineBreakMode:NSLineBreakByWordWrapping];
[textLabel setText:text];
[textLabel setFrame:CGRectMake(25, y, 275, MAX(size.height + 60, 44.0f))];
[textLabel setBackgroundColor:[UIColor clearColor]];
[cell addSubview:textLabel];
return cell;
}
更新计算单元格大小
-(float)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath {
float titleFontSize = 14.0f;
float offSet = 0;
NSString *text = @"";
if(indexPath.row == 0) {
text = question;
titleFontSize = 16.f;
offSet = 10;
}
else
text = answer;
CGSize constraint = CGSizeMake(285, 20000.0f);
CGSize size = [text sizeWithFont:[UIFont systemFontOfSize:titleFontSize] constrainedToSize:constraint lineBreakMode:NSLineBreakByWordWrapping];
CGFloat height = MAX(size.height + 40, 44.0f);
return height + offSet;
}
推荐答案
我过去遇到过这个问题，而且总是由于单元格高度不正确...单元格不一样，所以我们必须掌握这些代码.
I've had this problem in the past and it's always due to the cells height being incorrect... You've got quite a few instances where your two cells are not the same, so we are going to have to get a grip on that code.
int y
这个值也有点让我担心，因为它看起来将 textLabel 框架 origin.y 设置为 -20 ...如果您希望每个单元格中的 Y 偏移不同，但单元格的其余部分相同，没关系，但在这种情况下，我想我会建议为两种类型的单元格使用不同的 UITableViewCell 子类......并更改该子类中的所有标签属性等..
this value is also concerning me a little as it looks like it sets the textLabel frame origin.y to -20 ... if you want a different offset for Y in each cell but the rest of the cell is the same, that's fine, but in this case I think I'd suggest a different UITableViewCell subclass for the two types of cell... And change all the label properties etc inside that subclass..
所以...
为每种类型的单元格创建一个 UITableViewCell 子类，随意调用它们...例如 MYQuestionTableViewCell 和 MYAnswerTableViewCell
Make a UITableViewCell subclass for each type of cell, call them whatever you like... for example MYQuestionTableViewCell and MYAnswerTableViewCell
在单元格内 MYQuestionTableViewCell .h 文件
inside the cell MYQuestionTableViewCell .h file
#define TEXT_LABEL_WIDTH 285.0f
#define TEXT_LABEL_QUESTION_FONT_SIZE 16.0f
在那个单元格内 MYQuestionTableViewCell .m 文件做
inside that cell MYQuestionTableViewCell .m file do
- (id)initWithStyle:(UITableViewCellStyle)style reuseIdentifier:(NSString *)reuseIdentifier
{
self = [super initWithStyle:style reuseIdentifier:reuseIdentifier];
if (self) {
self.backgroundColor = [UIColor redColor];
self.clipsToBounds = YES; // just to make sure we're calculating the height correctly
// set up your textLabel etc. in here
self.textLabel.textColor = [UIColor whiteColor];
self.textLabel.font = [UIFont fontWithName:@"Helvetica-Bold" size: TEXT_LABEL_QUESTION_FONT_SIZE]];
}
return self;
}
-(void)layoutSubviews
{
[super layoutSubviews];
self.textLabel.frame = CGRectMake(0.0f, 0.0f, TEXT_LABEL_WIDTH, self.contentView.frame.size.height);
}
现在我们的 textLabel 将是任何单元格的高度......现在它只设置在一个地方，我们知道如果它不正确会出现问题.
Now our textLabel will be whatever the height of the cell is... Now it's set in only one place, we know where the issue will be if it's not correct.
在您的第二个 MYAnswerTableViewCell 子类中，您需要设置其他值
In your second MYAnswerTableViewCell subclass you'll need the other values set
.h
#define TEXT_LABEL_ANSWER_FONT_SIZE 14.0f
.m
与另一个单元格相同，但它的属性值发生了变化
same as the other cell but changing for it's property values
因为您还在两个不同的单元格中使用了不同的字体...使用开关可能更容易...但我会尽量保持它与您之前所做的类似...这种加倍代码是造成混乱的原因，但有时这是不可避免的..我们会尽量保持简单.
As you are also using different fonts in the two different cells... it might be easier to use a switch.. but I'll try to keep it similar to what you were doing before.. this sort of doubling up of code is the cause of the confusion, but sometimes it's unavoidable.. We'll just try to keep it as simple as we can.
-(CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath {
CGFloat offSet = 0.0;
NSString *text = @"";
UIFont *fontUsed = nil;
if(indexPath.row == 0) {
fontUsed = [textLabel setFont:[UIFont fontWithName:@"Helvetica-Bold" size: TEXT_LABEL_QUESTION_FONT_SIZE]];
text = question;
offSet = 10.0f;
}
else
{
fontUsed =[UIFont systemFontOfSize:TEXT_LABEL_ANSWER_FONT_SIZE];
text = answer;
}
NSLog (@"TEXT: %@",text); // checking if the text is set...
CGSize constraint = CGSizeMake(TEXT_LABEL_WIDTH, HUGE_VALF); // personally I prefer HUGE_VALF for that
CGSize size = [text sizeWithFont:fontUsed constrainedToSize:constraint lineBreakMode:NSLineBreakByWordWrapping];
CGFloat height = MAX(size.height + 40.0f, 44.0f); // 40.0f for padding?
return height + offSet;
}
除非需要，否则不应向单元格添加标签，它们随附了一些标签...现在您的 cellForRow 看起来像这样
You shouldn't be adding labels to a cell unless you need to, they come with some provided... now your cellForRow can look like this
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *QuestionCellIdentifier = @"QuestionCell";
static NSString *AnswerCellIdentifier = @"AnswerCell";
if (indexPath.row == 0)
{
MYQuestionTableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:QuestionCellIdentifier];
if (!cell)
cell = [[MYQuestionTableViewCell alloc]initWithStyle:UITableViewCellStyleDefault reuseIdentifier:QuestionCellIdentifier];
cell.textLabel.text = question;
return cell;
}
MYAnswerTableViewCell *cell = [tableView dequeueReusableCellWithIdentifier: AnswerCellIdentifier];
if (!cell)
cell = [[MYAnswerTableViewCell alloc]initWithStyle:UITableViewCellStyleDefault reuseIdentifier:AnswerCellIdentifier];
cell.textLabel.text = answer;
return cell;
}
你还需要
#import "MYQuestionTableViewCell.h"
#import "MYAnswerTableViewCell.h"
在视图控制器的顶部
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